It appears that most birds do not normally show signs of infection with WNV. They do however, serve as natural reservoirs of the virus, and can pass the virus to feeding mosquitoes. During the New York area outbreak however, there was a large die-off of American crows. This was seen in many counties in New Jersey, and as far west as Hunterdon County, where two infected crows were identified. Other species of birds, including red tail hawks and blue jays, have been reported to show signs of Illness ranging from encephalitis to death.
Domestic animals such as dogs and cats do not appear to be at special risk of infection however, the virus was isolated from one feral cat in Union County, NJ. It is possible that pets could become infected by eating dead infected birds, but this is still unproven. Infected animals should receive standard veterinary care. Full recovery from the infection is likely.
Data suggest that while horses are susceptible to WNV, most will recover from the infection. However, federal investigations determined that WNV was responsible for several deaths of horses on Long Island in 1999. Horses become infected in the same way humans do, from the bite of an infected mosquito. There is no evidence of 'horse-to-horse' or 'horse-to-person' transmission of the WNV. Vaccines for other types of equine encephalitis are most likely not effective against WNV.